<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    var bulbSwitch = function (n) {
      return Math.floor(Math.sqrt(n + 0.5));
    };
    console.log(bulbSwitch(3));
  </script>

</body>

</html>